The problem is already one notification is placed on the notification area with some HTML message. Now I'm trying to show the new one using the above code snippet. the notification will appeared as I expected.But the old HTML message shows the raw html.How can I fix this issue?

In this attachment image earlier inside the span its shows link.After implement second warning message its showing raw html content like span details

Okay. Then MS must have changed something in the internal function itself. Sorry I don't have anything else to suggest regarding this method. As suggested above, you can use the normal alert if that fits your requirement.